Production of fibrous cellulose ethers using iodide salts as catalysts



United States Patent 3,395,971 PRODUCTION OF FIBROUS CELLULOSE ETHERS USING IODIDE SALTS AS CATALYSTS Ricardo H. Wade, Metairie, and Clark M. Welch and Howard P. Bennett, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Jan. 29, 1964, Ser. No. 341,141 14 Claims. (Cl. 8-120) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the production of fibrous cellulose ethers using organic and inorganic iodide salts to accelerate the etherification reaction.

The primary object of this invention is to provide an improved process for the production of highly substituted, thermoplastic, rot-resistant cellulose fibers, yarns and fabrics, and also crosslinked ethers of cellulose in fiber, yarn and fabric form that exhibit enhanced resiliency and dimensional stability. For textile purposes, it is highly advantageous to preserve the fiber structure and high molecular weight of cellulose as it occurs in cotton, wood pulp, ramie, flax, jute and hemp, and in fibrous regenerated cellulose such as spun rayon, to all of which the present processes are applicable. The processes described here are found to produce a high degree of substitution of cellulose within short periods of reaction, thus minimizing degradative side reactions which in slow etherification processes cause tendering, embrittlement, and stiffening of yarns and fabrics, and which in some cases produce solution of the fibers in the reaction medium, destroying the textile qualities of the cellulose.

Advantages of the catalytic processes described herein lie not only in the high rate of etherification obtained, which often exceeds the rate of non-catalyzed etherification by 40500%, but also in the fact that the noncatalyzed etherification may come to a halt after less than two hydroxyl groups in every three anhydroglucose units of the cellulose has been etherified (Klein, Stanonis, Harbrink and Berni, Textile Research 3., 28659 (1958), Table IV), whereas higher degrees of substitution are often reached in the catalyzed processes of this invention.

The most general and widely used method of cellulose etherification is through the treatment of cellulose with sodium hydroxide to give a highly swollen and chemically activated material, soda cellulose, which in turn can be heated with an organic halide to form the cellulose ether. Organic chlorides have generally been preferred to the corresponding bromides or iodides because of the low cost and ready availability of the former, but in a number of cases the chlorides react too slowly with cellulose to be practical. The present invention overcomes this difficulty by the use of iodide salts which accelerate the etherification of cellulose by organic chlorides. The processes of this invention may be represented as follows:

Cell-OH MOH I Cell-OM H O Here Cell-OH is a portion of a cellulose chain, M is an alkali metal atom, X is a catalyst chosen from the class consisting of alkali metal iodides and aliphatic quaternary ammonium iodides, and RC1 is an organic monoor polychloride having in each molecule at least one functional group of the structure Where R and R" may be the same or different organic 3,395,971 Patented Aug. 6, 1968 ice radicals or segments of the same ring and are chosen from the class consisting of hydrogen, alkyl, cycloalkyl, aralkyl, aryl, alkenyl, cycloalkenyl and alkynyl radicals.

Where the organic chloride has but one cellulose-reactive chlorine atom per molecule, the resulting cellulose ether is found to exhibit thermoplasticity properties which enable coiling and crimping to be heat-set in yarns of the material. Such coiling and crimping imparts elasticity to the yarns. Where an unsaturated organic chloride is used, the carbon-to-carbon multiple linkage serves as a locus for the graft polymerization of monomers such as styrene onto the cellulose ether, by means of heat, irradiation, oxygen, or peroxides, to increase the abrasionand waterresistance of the cellulose. Moreover heat and oxygen are known to cause crosslinking of such unsaturated ethers of cellulose, imparting increased dimensional stability and resistance to chemical attack. Where the organic chloride contains at least two reactive chlorine atoms per molecule, crosslinking occurs directly in the course of etherification, imparting resistance to stretching and to shrinkage.

It has been found that mixtures of two or more different organic chlorides may be employed as the etherifying agent to give mixed ethers of cellulose having selected combinations of special properties. The catalysts of the present invention are fully as elfective on a mixture of organic chlorides as on the organic chlorides used singly. In some instances, a synergistic effect occurs between such combinations of organic chlorides.

Although other iodide salts soluble in alkali metal hydroxides may be employed as the catalyst in this process, the alkali metal iodides are preferred because of their exceptional freedom from precipitation reactions, their lack of color, and their low cost.

The procedure employed in the present proccesses is simple and capable of many variations applicable to different forms of cellulose and types of organic chlorides. The cellulosic fiber, yarn or fabric is treated with an aqueous solution containing from about 8% to about 33% of the alkali metal hydroxide and from about 5% to about 25% of the alkali metal iodide or aliphatic quaternary ammonium iodide catalyst. After the cellulose has soaked in this aqueous solution for a period of one to sixty minutes at ordinary temperature, it may be drained of excess solution and is then heated with the organic chloride alone or in the presence of an inert water-immiscible diluent at a temperature in the range of -180 C., preferably at 80-130" C. when the pressure is one atmosphere, to avoid excessive losses of volatile reactants and diluents, and for a period of time which depends on the degree of cellulose substitution desired, but which ordinarily ranges from fifteen minutes to six hours. At temperatures below 80 C., the catalyst is relatively ineffective. After the reaction has been completed, the etherified cellulosic fibers, yarns or fabric may be freed of excess organic halide, alkali and salts by washing with water and water-miscible organic solvents. Hot alkanolamines are particularly effective in the quaternization and removal of traces of organic halides which if left on the cellulosic derivatives not only may impart an irritating odor, but may through gradual hydrolysis give traces of hydrochloric acid which tender the said cellulosic derivatives.

In carrying out the reaction of organic chlorides with cellulose by the processes of this invention, the presence of water-miscible organic diluents for the alkali or the organic chloride is to be avoided. It has been found preferable that the organic chloride remain in a separate phase from the aqueous alkali and that the organic chloride not be solubilized in the aqueous alkali, as such solubilization results in hydrolysis of the organic chloride by the alkali and this interferes with the desired etherification of cellulose. The effectiveness of the iodide catalysts is especially novel and unique in that these ionic catalysts remain in the aqueous phase which is distinct and separate from the liquid organic phase containing the organic chloride and is also separate from the solid cellulosic phase. Such catalysis in a three-phase heterogeneous system is unusual.

The following examples were chosen merely to illustrate the present invention, and are not indicative of all the procedures, catalysts, and organic halides which can be employed in the processes of this invention. All per centages are by weight.

Example 1.Benzylation of cellulose at various temperatures A number of cotton yarn samples were benzylated under varying reaction conditions. The samples were prepared as skeins, and were reacted separately. The most representative samples were selected and tabulated below. The general scheme of preparation of this series was as follows.

A skein of commercially mercerized 7/2 linker yarn, weighing 6 to 7 grams, was immersed, slack, in an aqueous 23% sodium hydroxide containing a selected quantity of potassium iodide. The skein was allowed to soak for minutes at room temperature to C.), then centrifuged to a wet pickup of about 200% to 250%. The sample was then placed in a test tube fitted with an air condenser, and was covered with approximately 60 ml. of reagent grade benzyl chloride. The reaction tube was then placed in a thermostatically controlled heating bath (varying temperatures are shown in Table I) for about to 60 minutes. The reaction was quenched by immersing the sample in triethanolamine (TEA) at room temperature, whereby any remaining organic chloride was destroyed by heating in the said TEA at a temperature of about 110 C. for about 20 minutes. The sample was removed from the reaction tube and submitted to three 200 ml. washings in methanol, followed by a 15-minute wash in running tap water at room temperature, and drying at the prevailing humidity.

Each skein in this series was submitted to a similar procedure. The varying reaction conditions as well as the weight gain, degree of substitution (D.S.), and breaking strength of the final product are recorded in Table I.

Untreated yarn, Breaking Strength, 7.6 lbs. Untreated yarn mercerized with 23% NaOH, Breaking Strength, 10.6 lbs.

The presence of potassium iodide accelerated the reaction of benzyl chloride with the cellulose by approximately 100% at each temperature studied. The degree of substitution imparted had no appreciable effect on the overall degree of acceleration. At moderate reaction temperatures the breaking strength of the treated yarns, even at a degree of substitution as high as 0.7, was as great as that of untreated yarn.

Example 2.-Benzylation of cellulose at various sodium hydroxide concentrations A number of cotton yarn samples were benzylated under varying reaction conditions. More specifically, the NaOH concentration was varied from 8% to 23%. The concentration of the NaI was in one case 15%, and in all other reactions either 20% or omitted for comparison. The most representative samples were selected and tabulated below. The general scheme of preparation of this series follows.

A skein of 12/3 scoured cotton yarn, weighing 3 to 5 grams, was immersed, slack, in aqueous sodium hydroxide of varying concentration containing a selected quantity of sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of about 200%. The sample was placed in a test tube fitted with an air condenser, and was covered with 60 ml. of benzyl chloride. Then the reaction tube was placed in a thermostatically controlled heating bath at 115 C. for 30 minutes. The reaction was quenched in TEA and processed beyond this point as in Example 1.

Each skein in this series was submitted to a similar procedure. The varying reaction conditions as well as the weight gain, degree of substitution (D.S.), and the breaking strength of the final products are recorded in Table II.

TABLE II NaI Weight Breaking NaOH (percent (percent) Gain D.S. Strength (percent) (lbs) Untreated yarn, Breaking Strength, 5.4 lbs. Untreated yarn mercerized with 23% N a011, Breaking Strength, 7.1 lbs.

It is evident that at each concentration of sodium hydroxide studied, the presence of sodium iodide increased the rate of benzylation, the rate of increase being from to 200% at the highest iodide concentration. Moreover, the benzylated yarns at the different degrees of substitution prepared were as strong as untreated yarn.

Example 3.Benzylation of cellulose in the presence of various alkalies and alkali metal halides A number of cotton yarn samples were benzylated under varying reaction conditions. The metal hydroxides used were sodium hydroxide and potassium hydroxide. The metal halides employed in this series were sodium iodide, sodium bromide, and potassium iodide. The most significant samples were selected for tabulation below. The general method of preparation was as follows.

A skein of 12/3 scoured cotton yarn, weighing 3 to 5 grams, was immersed, slack, in a solution consisting of an alkali metal hydroxide, an alkali metal halide, and water. After 30 minutes the skeins were removed and centrifuged to a wet pickup of about 200%. The sample was placed in a test tube fitted with an air condenser, and was covered with 60 ml. of benzyl chloride. Then the reaction tube was placed in a thermostatically controlled heating bath at C. for 30 minutes. The reaction was quenched in TEA and processed beyond this point as in Example 1.

Each skein in this series was submitted to a similar procedure, and the pertinent data of the series is presented in Table III.

The data show that the catalytic elfect of iodide salts is a unique property of iodide ions, since other halide ions do not act as catalysts and since the effect is independent of which alkalies or which cations are present.

Example 4.Reaction of 1,4-bis(chloromethyl)benzene with cellulose A skein, weighing 4.4 grams, of 12/3 scoured cotton yarn was immersed, slack, in an aqueous solution containing 23% sodium hydroxide and sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 200%. The sample was then immersed in a molten mixture consisting of 40 grams of 1,4-bis(chloromethyl)benzene and 20 grams of tetralin in a test tube fitted with an air condenser, the tetralin serving to lower the melting point of the organic dihalide below the reaction temperature used. Then the reaction tube was placed in a thermostatically controlled heating bath at 115 C. for 30 minutes. The reaction was quenched in TEA and processed beyond this point as in Example 1.

The skein was allowed to dry at room temperature; extracted with boiling dimethylformamide; washed with water, and again allowed to dry at room temperature. The yarn had a weight gain of 23% over the original skein, corresponding to a degree of substitution of 0.37 p-xylylene groups per anhydroglucose unit. It fluoresced a yellow color under ultraviolet light, and its insolubility in 0.5 M cupriethylenediamine solution indicated that a significant degree of crosslinkage was obtained in the derivative. The derivative had a yarn breaking strength of 4.4 pounds, as compared with 4.6 pounds for the untreated yarn, and 6.8 pounds for the untreated yarn which had been immersed in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide for 30 minutes and washed and dried.

In a comparative reaction wherein the sodium iodide was omitted the weight gain of the finished product was 14%, and the yarn breaking strength only 3.8 pounds. Correlated to this reaction is another comparative reaction wherein only 23% sodium hydroxide was present, and the breaking strength of the yarn which was immersed for 30 minutes was 6.2 pounds.

Example 5.-Reaction of a mixture of benzyl chloride and 1,4-bis(chloromethyl)benzene with cellulose A skein, weighing 4.4 grams, of 12/3 scoured cotton yarn was immersed, slack, in an aquenous solution containing 23% sodium hydroxide and 20% sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 200%. The sample was then immersed in a mixture of 25 grams of 1,4-bis(chloromethyl)benzene and 50 grams of benzyl chloride in a test tube fitted with an air condenser. The reaction tube was placed in a thermostatically controlled heating bath at 115 for minutes. The reaction was quenched in TEA and processed beyond this point as in Example 1. The product had a weight gain of 46% over the untreated cotton, and the yellow fluorescence of the product under ultraviolet light indicates that some of the 1,4-bis(chloromethyl)benzene had reacted with the cellulose.

In a comparative reaction wherein 1,4-bis (chloromethyl)benzene was not in mixture with benzyl chloride the weight gain was only 34%.

In a comparative reaction wherein only the sodium iodide was omitted the weight gain of the product was 26%, which shows that sodium iodide in the previous instance accelerated the reaction by 77%.

Example 6.Reaction of cellulose with l-chloro-methylnaphthalene A skein of 12/3 scoured cotton yarn, weighing 5.1 grams, was immersed, slack, in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 250%. The sample was then placed in a test tube fitted with an air condenser, and was covered with 60 ml. of l-chloromethylnaphthalene. The reaction tube was then placed in a thermostatically controlled heating bath at 115 C. for 2 hours. The reaction was quenched in TEA and processed beyond this point as in Example 1. The derivative had a weight gain of 66% over the untreated cotton, corresponding to a degree of substitution of 0.76 (l-naphthyl)methyl group per anhydroglucose unit.

In the comparative reaction wherein the potassium iodide was not present the weight gain of the finished product was 47%.

The thermoplastic character of the derivative was observed upon coiling the said product tightly around a glass rod, heating the coil at 180 C. for 25 minutes, and allowing to cool. The coiling was found to be permanently set by the heat and could not be removed by repeated stretching. An untreated cotton yarn which was submitted to the same treatment did not show the same characteristic. The coiling of the untreated yarn was promptly removed by elongation.

Example 7.Reaction of cellulose with 1,4-dichloro-2-butene A skein of 12/3 scoured cotton yarn, weighing 3.9 grams, was immersed, slack, in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 200%. The sample was then placed in a large test tube fitted with an air condenser, and was covered with a solution consisting of 15 grams of 1,4- dichloro-Z-butene and 45 grams of tetralin. The reaction tube was then placed in a thermostatically controlled heating bath at 115 for 30 minutes. The reaction was quenched and the processing of the sample was continued as in Example 1. The derivative had a Weight gain of 15.4% over the untreated cotton, corresponding to a degree of substitution of 0.5 of 1,2-ethylenedimethyl crosslinks per anhydroglucose unit. The final weight was not changed by extraction with boiling tetrahydrofuran, a polymer solvent.

The treated yarn was insoluble in aqueous 0.5 M cupriethylenediamine solution. The insolubility of the product was indicative of the existence of crosslinks. The derivative had a breaking strength of 2.6 pounds, as compared with 4.6 pounds for the untreated yarn, and 6.8 pounds for the untreated yarn which had been immersed in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide for 30 minutes and washed and dried.

In a comparative reaction wherein the sodium iodide Was omitted the weight gain of the finished product was 10.3%.

Example 8.-Reaction of cellulose with 1,3-dichloropropene A skein of 12/3 scoured cotton yarn, weighing 4.0 grams, was immersed, slack, in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 225%. The sample was placed in a test tube fitted with an air condenser, and covered with a solution consisting of 20 grams of 1,3-dichloropropene and 40 grams of tetralin. The reaction tube was then placed in a thermostatically controlled heating bath at C. for 30 minutes. The reaction was quenched in TEA and processed beyond this point as in Example 1. The derivative had a weight gain of 30% over the untreated cotton, and the final weight was not changed by extraction with boiling tetrahydrofuran, a polymer solvent.

The treated yarn was insoluble in an aqueous 0.5 M cupriethylenediamine solution. The insolubility of the product was indicative of the existence of crosslinks.

The breaking strength of the yarn derivative was 1.9 pounds, as compared with 4.6 pounds for the untreated yarn, and 6.8 pounds for the untreated yarn which had been immersed in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide for 30 minutes and washed and dried.

A chlorine analysis of the derivative indicated a content of 8.7% chlorine, corresponding to a degree of substitution of 0.5 and 3-chloroallyl groups per anhydroglucose unit of the cellulose. The infrared spectrum of this derivative showed peaks which are characteristic of the cellulose structure and of the carbon-to-carbon double bond, which peaks correlate to the peaks of the theoretical 3-chloroallyl ether derivative of cellulose.

In the comparative reaction wherein the sodium iodide was omitted, the weight gain of the finished product was 16%, and the yarn breaking strength only 2.2 pounds, while the chlorine content was 5.3%. The iodide salt used in the derivative preparation by the process of this invention accelerated the etherification by 88%.

Example 9.--Reaction of cellulose with 1,3-dichloropropane A skein of 12/3 scoured cotton yarn, weighing 4.0 grams, was immersed, slack, in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide. After 30 minutes the skein was removed and centrifuged to a wet pickup of 200%. The sample was then placed in a test tube fitted with an air condenser, and covered with 60 ml. of 1,3-dichloropropane. The reaction tube was then placed in a thermostatically controlled heating bath at 115 C. for 30 minutes. The reaction was quenched and the processing of the sample was continued as in Example 1. The derivative had a weight gain of 7.5% over the untreated cotton, corresponding to a degree of substitution of 0.30 of 1,3-trimethylene crosslinks per anhydroglucose unit. The final weight was not changed :by extraction with boiling tetrahydrofuran, a polymer solvent.

The treated yarn was insoluble in aqueous 0.5 M cupriethylenediamine solution. The insolubility of the product was indicative of the existence of crosslinks. The derivative had a breaking strength of 5.4 pounds, as compared with 4.6 pounds for the untreated yarn, and 6.8 pounds for the untreated yarn which had been immersed in an aqueous solution containing 23% sodium hydroxide and 20% sodium iodide for 30 minutes and washed and dried.

In a comparative reaction wherein the sodium iodide was omitted the weight gain of the finished product was 2.6%.

We claim:

1. A process for etherifying fibrous cellulosic material comprising:

(a) wetting the said fibrous cellulosic material with an aqueous solution containing an alkali metal hydroxide and an alkali metal iodide, and

(b) reacting the wet cellulosic material with an organic chloride having at least one functional group of the structure where R and R" are selected from the group consisting of hydrogen, alkyl, cycloalkyl, aralkyl, aryl, alkenyl, cycloalkenyl, and alkynyl radicals.

2. A process for etherifying fibrous cellulosic material comprising:

(a) wetting the said fibrous cellulosic material with an aqueous alkali metal hydroxide solution about from 8% to 33% by weight, selected from the group consisting of sodium hydroxide and potassium hydroxide mixed with an alkali metal iodide about from 5% to 25% by weight, selected from the group consisting of potassium iodide and sodium iodide, and

(-b) reacting the wet cellulosic material to a degree of substitution of about from 0.05 to 1.0 with an organic chloride selected from the group consisting of 1,4- bis(chloromethyl)benzene, benzyl chloride, 1- chloromethylnaphthalene, 1,4-dichloro-2-butene, 1,3- dichloropropene, and 1,3-dichloropropane.

3. The process of claim 2 wherein the alkali metal hydroxide is sodium hydroxide.

4. The process of claim 2 wherein the alkali metal hydroxide is potassium hydroxide.

5. The process of claim 2 wherein the organic chloride is l,4-bis(chloromethyl)benzene.

'6. The process of claim 2 wherein the organic chloride is benzyl chloride.

7. The process of claim 2 wherein the organic chloride is 1-chloromethylnaphthalene.

8. The process of claim 2 wherein the organic chloride is 1,4-dichloro-2-butene.

9. The process of claim 2 wherein the organic chloride is 1,3-dichloropropene.

10. The process of claim 2 wherein the organic chloride is 1,3-dichloropropane.

11. The (l-naphthyl)methyl ether of fibrous cellulose, as a polymeric material, wherein the said fibrous cellulose is substituted to the extent about from 0.05 to 0.75 (1- naphthyl)methyl group per anhydroglucose unit, the cellulosic ether having retained the fibrous structure and textile properties common to the original native cellulose.

12. The 3-chloroallyl ether of fibrous cellulose, as a polymeric material, wherein the said fibrous cellulose is substituted to the extent about from 0.05 to 0.5 of 3- chloroallyl group per anhydroglucose unit, the cellulosic ether having retained the fibrous structure and textile properties common to the original native cellulose.

13. The 1,3-trimethylene ether of fibrous cellulose, as a polymeric material, wherein the said fibrous cellulose is substituted to the extent about from 0.05 to 0.3 of 1,3- trimethylene group per anhydroglucose unit, the cellulosic ether retaining the fibrous structure and textile properties common to the original native cellulose.

14. The 1,4dichlorobutene ether of fibrous cellulose, as a polymeric material, wherein a 1,2-ethylenedimethyl group is introduced as a crosslinking entity of the chemically modified fibrous cellulose, and wherein the said fibrous cellulose is substituted to the extent about from 0.05 to 0.5 retaining the fibrous structure and textile properties common to the original native cellulose.

/ No references cited.

NORMAN G. TORCHIN, Primary Examiner.

J. CANNON, Assistant Examiner. 

1. A PROCESS FOR ETHERIFYING FIBROUS CELLULOSIC MATERIAL COMPRISING: (A) WETTING THE SAID FIBROUS CELLULOSIC MATERIAL WITH AN AQUEOUS SOLUTION CONTAINING AN ALKALI METAL HYDROXIDE AND AN ALKALI METAL IODIDE, AND (B) REACTING THE WET CELLULOSIC MATERIAL WITH AN ORGANIC CHLORIDE HAVING AT LEAST ONE FUNCTIONAL GROUP OF THE STRUCTURE 